This invention relates to abrasive products.
Abrasive compacts are well known in the art and are used extensively in industry for the abrading of various workpieces. They consist essentially of a mass of abrasive particles present in an amount of at least 70 percent, preferably 80 to 90 percent, by volume of the compact bonded into a hard conglomerate. Compacts are polycrystalline masses and can replace single large crystals in many applications. The abrasive particles of compacts are invariably ultra-hard abrasives such as diamond and cubic boron nitride.
Abrasive compacts generally contain a second phase or bonding matrix which contains a catalyst (also known as a solvent) useful in synthesising the particles. In the case of cubic boron nitride, examples of suitable catalysts are aluminium or an alloy of aluminium with nickel, cobalt, iron, manganese or chromium. In the case of diamond, examples of suitable catalysts are metals of Group VIII of the Periodic Table such as cobalt, nickel or iron or an alloy containing such a metal.
As is known in the art, diamond and cubic boron nitride compacts are manufactured under conditions of temperature and pressure at which the abrasive particle is crystallographically stable.
Abrasive compacts may be bonded directly to a tool or shank for use. Alternatively, they may be bonded to a backing such as a cemented carbide backing prior to being mounted on a tool or shank. Such backed compacts are also known in the art as composite abrasive compacts.
U.S. Pat. No. 4,224,380 describes a method of leaching out a substantial quantity of the catalyst from a diamond compact. The product so produced comprises self-bonded diamond particles comprising between about 70 percent and 95 percent by volume of the product, a metallic phase infiltrated substantially uniformly throughout the product, the phase comprising between about 0.05 percent and 3 percent by volume of the product, and a network of interconnected, empty pores dispersed throughout the product and defined by the particles and the metallic phase, the pores comprising between 5 percent and 30 percent by volume of the product. Leaching may be achieved by placing a diamond compact in a hot concentrated nitric-hydrofluoric acid solution for a period of time. This treatment with the hot acid leaches out the catalyst phase leaving behind a skeletal diamond structure. The leached product is said to be thermally more stable than the unleached product.
U.S. Pat. No. 4,124,401 describes and claims a polycrystalline diamond body comprised of a mass of diamond crystals adherently bonded together by a silicon atom-containing bonding medium comprised of silicon carbide and a carbide and/or silicide of a metal component which forms a silicide with silicon, the diamond crystals ranging in size from 1 micron to about 1000 microns, the density of the crystals ranging from at least about 70 percent by volume up to at least about 90 percent by volume of said body, said silicon atom-containing bonding medium being present in an amount ranging up to about 30 percent by volume of said body, said bonding medium being distributed at least substantially uniformly throughout the body, the portion of the bonding medium in contact with the surfaces of the diamond crystals being at least in a major amount silicon carbide and the diamond body being at least substantially pore-free. The metal component for the diamond body is selected from a wide group of metals consisting of cobalt, chromium, iron, hafnium, manganese, molybdenum, niobium, nickel, palladium, platinum, rhenium, rhodium, ruthenium, tantalum, thorium, titanium, uranium, vanadium, tungsten, yttrium, zirconium and alloys thereof. The polycrystalline diamond body is made under relatively mild hot pressing conditions and such that diamond intergrowth will not occur.
U.S. Pat. No. 4,151,686 describes a polycrystalline diamond body similar to that of U.S. Pat. No. 4,124,401 save that the bonding medium is comprised of silicon carbide and elemental silicon and the density of diamond crystals in the body ranges from 80 percent by volume to about 95 percent by volume of the body. Moreover, the polycrystalline abrasive bodies of this United States patent are made under higher applied pressure conditions, i.e. applied pressures of at least about 25 kilobars. The abrasive bodies are said to be useful on an abrasive cutting tool, nozzle or other wear-resistant part.
U.S. Pat. No. 3,234,321 describes diamond compacts having a second phase of titanium, vanadium, zirconium, chromium or silicon or an alloy of any of these metals with nickel, manganese or iron. The compacts are made by mixing the diamond particles with the metal, in powdered form, and subjecting the mixture to elevated conditions of temperature and pressure. One example uses silicon as the metal in an amount of 31.5 volume percent. The patent suggests that the compact may be suitably shaped and mounted for cutting and abrading hard materials.
The complete specification of South African Pat. No. 84/0053 describes an abrasive body which has high strength and an ability to withstand high temperature making it suitable as a tool insert for dressing tools and surface set drill bits. The body comprises a mass of diamond particles present in an amount of 80 to 90 percent by volume of the body and a second phase present in an amount of 10 to 20 percent by volume of the body, the mass of diamond particles containing substantial diamond-to-diamond bonding to form a coherent skeletal mass and the second phase containing nickel and silicon, the nickel being in the form of nickel and/or nickel silicide and the silicon being in the form of silicon, silicon carbide and/or nickel silicide. The abrasive bodies are made under conditions of elevated temperature and pressure suitable for diamond compact manufacture.